Grinding-machine



KRISTIAN MIDDELBOE, OE EREDERIKSEEEG. NEAEOOBENEAGEN, DENMARK, AssIeNora To E. L. sivrIDTH a CO., or NEW YORK, N. Y., A CORPORATION OE NEW JERSEY.

GRINDING-MACHINE.

Specification of Letters Patent.

Application `filed May 2S, 1910,'Seria1 No. 300,454. Renewed Marchk S, 1921. Serial No. 450,671.

To all whom z'tfmag/ concern:

Be it known that I, KRisTIAN MIDDELBOE, civil engineer, a subject of the King of Denmark, residing at 14 Thorvaldsensvej, Frederiksberg, near Copenhagen, Denmark, have invented certain new and useful Improvements in Grinding-Machines, of which the following is a specification, reference being had to the accompanying drawing, forming a part hereof. v

The invention relates to a grinding machine in which rolling grinding bodies are arranged between grinding guides forming a path for the grinding bodies, one of the guides being formed in sections and subjected to pressure to increase the grinding action.

Among the various machinesYwhich-have been employed for crushing and grinding materials two types are partigularly prominent, namely mills in which the crushing and grinding action is produced by the fall ofthe grinding bodies and mills 'in which the action is produced by the rolling action of the grinding bodies. Y

' In the former type of mill the material to be crushed and ground -imparts potential energy to loose grinding bodies by lifting them to a certainheight so that in falling from this height they effect thecrushing and grinding. Vhile mills'of this type have great advantages, they are dependent somewhat On the proper supply of the material to be treated and require considerable power even when running'idle.

In mills ofthe other type referred to in which thecruShing and grinding action is produced by rolling bodies coacting with guiding means and may be increased by centrifugal force acting on the rolling bodies or by loading them by weights or springs, the construction is more complicated and eX- pensive than in mills of the falling body type but this is compensated for'by the fact that they require less power to operate them particularly when the mill is running empty. The capacity of inillsof 'this type is`,`however, rather limitedlbecause'the number of grinding bodies employed is necessarily small and they must be of relatively large size and must move'in a path of relatively small diameter and at considerable speed so that there 'is a considerable waste of power in overcoming friction.

The present invention has for its object to provide a mill of the rolling body type in which theadvantages of this type of mill will be utilized and the disadvantages heretofore found in this type will be overcome and has particularly for its object to provide a mill of this type in which the grinding bodies roll between guidingsurfaces which do not rotate at the same speed.

. With the above described objects and other objects hereinafter explained in view my invention consists in' the construction and combination lof elements hereinafter described and claimed.

Referring to the drawings,

Figure 1 is a vertical sectional view on the plane of the axis of the operating shaft, and

Fig. 2 is a'horizontal sectional view on the line 2-'2 of Fig. l.

In'the construction shown a indicates a vertical operating shaft which may be driven by any convenient, means and b, b indicate a holder forloading blocks f, comprising an upper disk Z) and a lower disk b both keyed to the operating shaft. The loading blocks f are carried between the disks?) and o and are radially movable being provided vwith radial grooves to receive radial guide ribs g on the disks. The loading blocksf, here shown as four in number, are each provided on its periphery witha section c of an annular ring which forms the inner'guiding path4 for the grinding bodies hereshown as balls e. Theouter guide for the grinding bodies comprises a ringd which is supported on the inner face of a cylindrical casing lc by lugsd by which the outer 'face of the ring isso spaced away from the casingas to leave-spaces cl2 for free passage of ground material as hereinafter described. The balls e thus roll between the inner ring formed'by the sections c and the outer ring d 'and in contactv with them. rIhe sections o are each provided on their forward ends, that is the ends which are forward in the rotation, with a resilient portion c formed by cutting away-the inner surface Of the section so as to leave a space between it and the periphery of v,the loading block f, so that as this forward end of a section c comes in contact with a ball e it will yield'sufliciently to avoid any thrusting action on vthe ball.' The balls elare spaced apart by arms t' carried by andfeztending upward'froina spider 7L the hub of which has its bearing on the hub Q the lower holder disk Zn. c

Below the spider 7L is arranged a bottom plate or disk j which is carried by and rotates with the hub of the lower holder disk b. This bottom plate or disk j isof such diameter that its outer edge is only a slight distance from the inner face of the casing 7c so as to leave between it and the casing a narrow annular space j and it car qies on its under side a series of radial wings Zthe lower edges of which rotating a slight distance from the horizontally arranged bottom m of the casing act to produce a blower effect to suck air through openings 'a in the bottom m and force it upward through the annular space j and the spaces Z2 between the outer face of the outer ring Z and the casing.

A bearing o for the operating shaft L is formed in the bottom m. Through the top plate 7c of the casing extends a pipe 22 through which the material to be treated is introduced. rlhe lower end of this pipe surrounds but is spaced away from the hub of the upper holder disk so as to leave between it and the hub a passage of sutilcient size to admit material freely. ln the top plate 7c about the pipe j) is an annular opening Q for free escape of air.v

The upper edge of the outer ring Z is a substantial distance above the plane of the upper face of the upper holder disk Z). Material to be treated introduced through pipe y) falls on the upper face of the upper holder disk o and as this is rotated at considerable speed the material will7 by centrifugal action7 be thrown ofi1 the edge of the disk and -into the space in which the balls c are rolling. rlhe height of the upper edge of the outer ring d prevents any of the material from being thrown against ythe casing and insures its passing into the space in which the balls c are rolling. rlhe material thus supplied to the grinding ballsreceives its rst crushing as it passes downward through the space in which the grinding balls are rolling and falls on the bottom plate or disk j. As this is rotating with the shaft a and the parts keyed to it, it acts to throw the material outward by centrifugal action into the path of the air current created by the wings Z and, by this current, the material, now partially ground7 is carried upward through the spaces cl2 into the space above the outer ring (l and holder l) yll`his space being' quite large the air current passing through it to escape through the openings g loses its lifting force in this space to such an extent that it will permit the coarser particles to drop and will carry with it through the openings g only the very finely ground particles the coarser particles dropping' back into the space in which the balls c are rolling and being again subjected to their crushing and grinding action. This action will be repeated until the material is reduced to such a condition of fineness that it will be carried out of the mill by the air current7 the material thus carried out being, of course, treated to separate any material not of the required degree of iineness and which requires further grinding.

'lhe centrifugal action of the bottom plate or disk y' is of sullicient force to cause the finer particles of the ground material to separate from the coarser particles overcoming any tendency to adhere together so that the separation in the space above the upper ends of the spaces Z2 will be very complete.

ln the operation of the mill it will be understood that the material in the space in which the grinding balls roll is carried around with thems the centrifugal action tending to hold it against the outer ring, until it is reduced to such a degree of fineness that it is carried upward by the air current as described.

The loading blocks f and the sections c forming the inner guide ring carried by them can move only radially with respect to the holder disks and as these loading blocks are all of the saine size and weight they will exert a substantially equal pressure at all points against the grinding balls so that there will be no tendency of the balls to wear unevenly and get out of spherical form. The action of the inner ring formed of the sections c rolls them on the inner face of the outer ring the friction thus being rolling friction only except as regards the contact with the balls of the arms z' of the spider '7a where there will be sliding' friction. But as tie spider t is mounted to rotate freely and the arms i follow the balls without exerting any pressure against them, the slight amount of sliding friction is of little importance. The movement of the grinding balls is thus due to the rotation of the inner and the rapidity of their rotation is dependent on the speed of rotation of the operating shaft and the centrifugal action of the loading blocks due to their rotation with the shaft. By reason of their ro tation being thus dependent on the speed of rotation of the operating shaft and the fact that their crushing and grinding action is dependent on the speed of rotation and the centrifugal force developed rather than on the sii/.e or weight of the balls it is found possible to use effectively much smaller grinding bodies than can usually be einployed in mills of this type and it is found possible to regulate themill to produce any pressure desirable in crushing and grinding particular material or in reducing the mate# rial treated to any particular degree of iinenoss by merely varying the speed of rotaion` of the operating shaft. l

lt will of course be understood that l do not desire to be limited to the particular' described as it is obvious that many changes 1n the construction and arrangement of parts may be made without departing from the spirit of the invention.

Having thus described my invention what I claim is* 1. ln a grinding mill the combination with an outer guide and a series of grinding bodies adapted to roll in contact with the inner face of said outer guide, of an inner guide comprising radially movable sections having its periphery in contact with the grinding bodies, means for rotating the inner guide and for moving the sections outward against the grinding bodies, said sections being each provided on its forward end with a portion adapted to yield inwardly relatively to the rear portion of the section.

2. In a grinding mill the combination with an outer guide and a series of grinding bodies adapted to roll in contact with the inner face of said outer guide, of an inner guide comprising sections carried by radially movable loading blocks and having their outer faces in contact with the grinding bodies, means for rotating the loading blocks to cause them to move outward by centrifugal force to press the sections against the grinding bodies, said sections being each provided on its forward end with a portion adapted to yield inwardly relative to the rear portion of the section.

3. In a grinding mill the combination with an outer guide and a series of grinding bodies adapted to roll in contact with the inner face of the outer guide, of a rotary shaft, upper and lower holder disks carried o'n and rotating with the shaft, loading blocks between and rotating with the holder disks each carrying a section of an inner guide having its outer face in contact with the grinding bodies, said sections being each provided on its forward end with a portion adapted to yield inwardly relative to the rear portion of the section.

il. n a grinding mill the combination with an outer guide and a series of grinding bodies adapted to roll in contact with the inner face of the outer guide, of a rotary shaft, upper and lower holder disks carried on and rotating with the shaft, loading blocks between and rotating with the holder disks each carrying a section of an inner guide having its outer face in contact with the grinding bodies, the upper edge of the outer guide being above the level of the upper face of the upper holder disk, and means for leading the material to be treated the grinding bodies, a disk arranged to ro-' tate below the grinding bodies and to receive material ground by them, and means for forcing a current of air upward at thev edge of the disk.

6 In a grinding mill the combination with an outer guide and a series of grinding bodies adapted to roll in contact with the inner face of'said outer guide, of an inner guide comprising radially movable sections having its periphery incontact with the grinding bodies, means for rotating the inner guide and for moving the sections outward against the grinding bodies, a disk arranged to rotate below the grinding bodies and to receive material ground by them provided with wings tocreate a current of air and force it upward at the edge of the disk.

7. n a grinding mill the combination with an inclosing casing having an air inlet in its bottom and an air outlet in its top of an outer guide secured within the casing and so spaced therefrom as to leave passages between its outer face and the casing, a series of grinding bodies adapted to roll in contact with the inner face of said outer guide, an inner guide comprising radially movable sections having its Vperiphery in contact with the grinding bodies, means for rotating the inner guide and for moving the sections outward against the grinding bodies, a disk below the grinding bodies having its edge so arranged as to leave a narrow passage between it and the casing in line with the passages between the outer guide and the casing and means for causing a current of air upward through the passage at the edge of the disk, through the passages between the outer guide and the casing and out through the outlet in the top of the casing.

This specification signed and witnessed this 12 day of April, A. D. 1919.

KRISTIAN MIDDELBOE. Signed in the presence of- A. ToRsTnNsrAN, E. W. MrsKoN. 

